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16 November 2014

A350 lithium-ion batteries comparing with 787 system: double number of batteries but with more conservative power output and energy levels.

Airbus and supplier Saft have confirmed several key details of the A350-900’s rechargeable lithium-ion batteries which are soon to become the production standard.

Though incomplete, the details show Airbus and Saft designed the batteries with more conservative power output and energy levels than found on the 787 batteries that caused a 4-month grounding in 2013.

The grounding was lifted in May 2013 only after Boeing revised the installation design, although the architecture of the GS Yuasa-designed system remained the same.

Source: FlightGlobal

Though much heavier than the Boeing design, the Airbus approach is more cautious. Instead of the 787’s 2 batteries, Airbus will install 4 lithium-ion batteries in each A350-900. Each of the Saft batteries consists of 14 cells storing a combined 45Ah of energy and running at 3.6V. Yuasa batteries onboard the 787 consists of 8 cells storing a combined 72Ah of energy and running at 3.7V.

One of the 4 batteries is dedicated to starting the APU, and the 3 others will provide power to other components in the A350 electrical system, Airbus said.

Details of the A350’s lithium-ion batteries have been a closely held secret since Saft was identified as the supplier 6 years ago.

As the 787 entered the battery-induced grounding, Airbus said the A350 would first be certificated with more traditional nickel-cadmium batteries that would be replaced by the lithium-ion batteries by early next year, around MSN21 for Qatar Airways.

Unlike GS Yuasa, which has released a specification sheet on the 787 batteries (it uses a lithium cobalt oxide chemistry – which is considered the most reactive and inherently volatile electrolytes in lithium ion-based systems), Saft had never revealed the technical characteristics of the A350-900 battery; the voltage of the A350 battery appears to rule out lithium iron phosphate, which is the least volatile lithium-based chemistry. But Airbus could still be using other chemistries considered safer than lithium cobalt oxide, such as lithium nickel manganese oxide.

The A350 installation includes an “overboard venting system”. That system is now being reviewed by the European Aviation Safety Agency and the US Federal Aviation Administration.

“We are progressing well with EASA and FAA – also considering recommendations from the US National Transportation Safety Board – to certify the li-ion main batteries in order to offer them to our customers at a later stage,” Airbus said.

Based on the article “Airbus cautious on lithium battery design for A350” published in Flight Global.